The dietary vitamin B3, which encompasses nicotinamide (“Nam” or “NM”), nicotinic acid (“NA”), and nicotinamide riboside (“NR”), is a precursor to the coenzyme nicotinamide adenine dinucleotide (“NAD+”), its phosphorylated parent (“NADP+” or “NAD(P)+”), and their respective reduced forms (“NADH” and “NADPH,” respectively). Once converted intracellularly to NAD(P)+ and NAD(P)H, vitamin B3 metabolites are used as co-substrates in multiple intracellular protein modification processes, which control numerous essential signaling events (e.g., adenosine diphosphate ribosylation and deacetylation), and as cofactors in over 400 redox enzymatic reactions, thus controlling metabolism. This is demonstrated by a range of metabolic endpoints, which include the deacylation of key regulatory metabolic enzymes, resulting in the restoration of mitochondrial activity and oxygen consumption. Critically, mitochondrial dysfunction and cellular impairment have been correlated to the depletion of the NAD(P)(H)-cofactor pool, when the NAD(P)(H)-cofactor pool is present in sub-optimal intracellular concentrations. Vitamin B3 deficiency yields to evidenced compromised cellular activity through NAD(P)+ depletion, and the beneficial effect of additional NAD(P)+ bioavailability through NA, Nam, NR, and nicotinamide mononucleotide (“NMN”) supplementation is primarily observed in cells and tissues where metabolism and mitochondrial function have been compromised.
Despite extensive optimization of solution-based methodologies over many years for nucleotide preparation, difficulties and issues remain in the syntheses of nicotinoyl ribosides, the monophosphorylation of active hydroxyl groups thereof, and subsequent conjugation thereof, with respect to low yields and product stability and isolation from polar solvents. The current methodologies are also plagued by atom and energy inefficiency due, for example, to the use of large solvent excesses and the need for temperature-controlled reaction conditions.
The reported syntheses of nicotinamide riboside (NR) are becoming more scalable, but use corrosive and expensive reagents, and lengthy deprotection steps, and thus still display batch-to-batch quality variation, thereby presenting difficulties in maintaining good standards.
Partially protected nucleosides and nucleotides have found broad-ranging application in order to achieve improved bioavailability of the nucleoside and nucleotide parents. Such partial protection includes hydroxyl modifications with ester, carboxylate, and acetyl groups, in addition to the introduction of hydrolyzable phosphoramidate or mixed anhydride modification of the phosphate monoesters in the form of Protides and CycloSal derivatives. While the former type of protection has become more scalable, the modifications at the phosphorus center remain difficult to accomplish at scale, particularly on nucleosidic entities that are highly sensitive to changes in pH and that are readily degraded by heat.
Reduced nicotinamide riboside (“NRH”) has been consistently shown to be more efficient at increasing intracellular NAD+ levels, and surpasses nicotinamide riboside (NR) in that respect. While physiological and potentially therapeutic roles have not yet been examined due to a lack of material accessible in sufficient quantities for broad-ranging studies, it is anticipated that the phosphorylated forms of NRH and reduced nicotinic acid riboside (“NARH”), or derivatives thereof, could also have similar NAD+-boosting capacities.
The reported syntheses of reduced nicotinamide riboside (NRH) are becoming more widely available but remain conducted on small scales, using corrosive and expensive reagents, and lengthy deprotection steps, and thus still display batch-to-batch quality variation, thereby presenting difficulties in maintaining good standards. In the current description, reduced nicotinamide riboside (NRH) generally refers to “reduced pyridine” nucleus, more specifically, the 1,4-dihydropyridine compounds.
Synthetically, the preparation of 5′-nucleotides remains time-consuming, atom-inefficient, and costly, due to the need for numerous protection and deprotection steps. In these preparation methods, the chlorodialkylphosphate, tetraalkylpyrophosphate, chlorophosphite, or phosphoramidite reagents required are also expensive starting materials by virtue of their chemical functionalization and chemical instability, and therefore, consequently associated synthetic difficulties. Phosphorylation reaction conditions are difficult to control and often use non-approved or toxic organic solvents, thus limiting the market of the manufactured compounds.
One known alternative approach to the protection/deprotection method is to use phosphorus oxychloride (P(O)Cl3) (i.e., Yoshikawa conditions), however there are still drawbacks to this method, as follows. While not being bound by theory, in this method, polar trialkyl phosphate solvents, such as P(O)(OMe)3, are used in a large excess, which are believed to enhance reaction rates while limiting the undesirable reactivity of P(O)Cl3 as a chlorinating agent. Thus, it is believed that use of excess P(O)Cl3/P(O)(OR)3 is a better combination for the chemoselective 5′-O-phosphorylation of unprotected ribosides. However, the use of trialkyl phosphate solvents, such as P(O)(OMe)3, precludes their implementation for the preparation of materials for eventual human use, as this class of solvent is highly toxic (known carcinogen, non-GRAS approved) and is difficult to remove from the final polar products. See M. Yoshikawa et al., Studies of Phosphorylation. III. Selective Phosphorylation of Unprotected Nucleosides, 42 BULL. CHEM. SOC. JAPAN 3505 (1969); Jaemoon Lee et al., A chemical synthesis of nicotinamide adenine dinucleotide (NAD+), CHEM. COMMUN. 729 (1999); each of which is incorporated by reference herein in its entirety.
Nicotinamide adenine dinucleotide (NAD+) remains an expensive cofactor, and its commercial availability is simply limited by its complex chemical nature and the highly reactive pyrophosphate bond, which is challenging to form at scale.
Nicotinoyl ribosides such as nicotinamide riboside (NR) and nicotinic acid riboside (“NAR”), nicotinamide mononucleotide (NMN), and NAD+ are viewed as useful bioavailable precursors of the NAD(P)(H) pool to combat and treat a broad range of non-communicable diseases, in particular those associated with mitochondrial dysfunction and impaired cellular metabolism. Optimizing the large-scale syntheses of these vitamin B3 derivatives is therefore highly valuable to make these compounds more widely available to society both in terms of nutraceutical and pharmaceutical entities.
Reduced nicotinoyl ribosides, such as reduced nicotinamide riboside (NRH), reduced nicotinic acid riboside (NARH), reduced nicotinamide mononucleotide (“NMNH”), reduced nicotinic acid mononucleotide (“NaMNH”), and reduced nicotinamide adenine dinucleotide (“NADH”) are viewed as useful bioavailable precursors of the NAD(P)(H) pool to combat and treat a broad range of non-communicable diseases, in particular those associated with mitochondrial dysfunction and impaired cellular metabolism. Optimizing the large-scale syntheses of these vitamin B3 derivatives is therefore highly valuable to make these compounds more widely available to society, both in terms of nutraceutical and pharmaceutical entities.
Crystalline forms of useful molecules can have advantageous properties relative to the respective amorphous forms of such molecules. For example, crystal forms are often easier to handle and process, for example, when preparing compositions that include the crystal forms. Crystalline forms typically have greater storage stability and are more amenable to purification. The use of a crystalline form of a pharmaceutically useful compound can also improve the performance characteristics of a pharmaceutical product that includes the compound. Obtaining the crystalline form also serves to enlarge the repertoire of materials that formulation scientists have available for formulation optimization, for example by providing a product with different properties, e.g., better processing or handling characteristics, improved dissolution profile, or improved shelf-life.
WO 2016/014927 A2, incorporated by reference herein in its entirety, describes crystalline forms of nicotinamide riboside, including a Form I of nicotinamide riboside chloride. Also disclosed are pharmaceutical compositions comprising the crystalline Form I of nicotinamide riboside chloride, and methods of producing such pharmaceutical compositions.
WO 2016/144660 A1, incorporated by reference herein in its entirety, describes crystalline forms of nicotinamide riboside, including a Form II of nicotinamide riboside chloride. Also disclosed are pharmaceutical compositions comprising the crystalline Form II of nicotinamide riboside chloride, and methods of producing such pharmaceutical compositions.
In view of the above, there is a need for processes that are atom-efficient in terms of reagent and solvent equivalency, that bypass the need for polar, non-GRAS (“generally recognized as safe”) solvents, that are versatile in terms of limitations associated with solubility and reagent mixing, that are time- and energy-efficient, and that provide efficient, practical, and scalable methods for the preparation of nicotinoyl ribosides, reduced nicotinoyl ribosides, modified derivatives thereof, phosphorylated analogs thereof, and adenylyl dinucleotide conjugates thereof.
In view of the above, there is a need for novel crystalline forms of nicotinoyl ribosides, reduced nicotinoyl ribosides, modified derivatives thereof, phosphorylated analogs thereof, and adenylyl dinucleotide conjugates thereof.